1. Field of the Invention
The present invention relates to a booster pump for a reverse osmosis water purification system.
2. Description of Related Art
Reverse osmosis (RO) water purification systems contain an osmotic membrane that removes impurities from a source of feedwater. RO systems require a relatively high water pressure to push the feedwater through the osmotic membrane. For this reason, RO systems typically include a pump to increase the feedwater pressure. Conventional RO pumps are driven by an electric motor which receives power from a dedicated power source or a municipal power outlet. Consequently, electric driven pumps require access to some type of electrical power. Additionally, electric driven pumps are relatively expensive to produce and repair. The consumption of electric power also increases the cost of operating the RO system.
U.S. Pat. Nos. 4,836,924 and 5,000,845 issued to Solomon, disclose a mechanical booster pump for a reverse osmosis water purification system. The Solomon booster pump contains a spring return piston that is driven by the pressure of the feedwater. The piston has a first head located within an inlet/reversing chamber of the pump and a second head that is located within a pump outlet chamber. The area ratios of the piston heads is such that the introduction of feedwater to the inlet chamber will stroke the piston and pressurize feedwater within the outlet chamber.
The Solomon pump also contains a spring actuated control valve that opens when the piston reaches a predetermined stroke position. Feedwater flows into the reversing chamber when the control valve is opened. The force of the piston return spring and the pressure of the feedwater within the reversing chamber push the piston back to the return position, wherein the valve closes and the cycle is repeated.
The spring needed to open the control valve of the Solomon pump requires additional energy to close the valve. The additional energy required to close the control valve lowers the pressure boost ratio of the pump. The control valve is also subject to wear, resulting in an improper seating of the valve. Improper valve seating may reduce the pressure ratio of the pump. It has also been found that the Solomon pump requires an accumulator to minimize the pressure fluctuations between strokes. It would be desirable to have a booster pump which did not have all of the above listed disadvantages.